<!DOCTYPE html>
<html lang="en">
    <head>
        <meta charset="UTF-8" />
        <meta http-equiv="X-UA-Compatible" content="IE=edge" />
        <meta name="viewport" content="width=device-width,initial-scale=1.0" />
        <title>Document</title>
    </head>
<body>
    <!-- 单页应用 -->
    <div id = 'app'>
        <!-- 插值表达式，声明式渲染 -->
       <h1> {{title}}</h1>
       <p>欢迎{{user.username}}</p>
    </div>
<script src = "vue.js"></script>
<script>
    new Vue({
        el:'#app' ,//使用css3选择器语法 指定element元素
        data: {
            title: 'first vue程序',
            user :{
                username: 'leaf',
                age: 18
            }
        }
    })
</script>
</body>
</html>